permaculture

["Kirby Fry" <peace@totalaccess.net>]

Hi All,

Below is a short, rather technical article about the accumulation of Carbon
and Nitrogen in grasslands and woodlands.  I can't exactly make sense of it.
Maybe someone here can.

The more I scan the Internet for articles about invasive native woodlands,
however, the more I see that it is a highly charged political issue.
Mainly, large cities are advocates of brush control because more water will
then be yielded for municipal consumption.  Cattlemen are also strong
political advocates of brush control along with the native plant and
restoration societies.

* * * * *

Rates of Soil Carbon and Nitrogen Accumulation During Succession From
Grassland to Woodland in a Subtropical Savanna Ecosystem

T.W. Boutton and S.R. Archer. 1998. Symposium on "How Much Carbon Can Soils
Sequester?". Soil Science Society of America Meeting (Baltimore, MD),
Abstracts p. 218.

Grasslands have been replaced by subtropical woodlands dominated by Prosopis
glandulosa and other highly productive, N-fixing woody legumes in southern
Texas during the past 100 y. To test the hypothesis that soil C and N would
accumulate during woodland development, we quantified those elements in
remnant grasslands, and in woodlands ranging from 10-110 y in age. Soil C
and N (0-20 cm) were significantly greater in wooded landscape elements (C =
2467-5213 g m-2 ; N = 233-455 g m-2) than in grasslands (C = 2122 g m -2 ; N
= 150 g m -2 ). Rates of C accumulation in the top 20 cm of the profile were
linear over the past 100 y, ranging from 20 g C m -2 y -1 in upland
woodlands to 50 g C m -2 y -1 in lowland woodlands. Accrual of N was also
linear, ranging from 2 g N m -2 y -1 in upland woodlands to 5 g N m -2 y -1
in lowland woodlands. Simultaneously, soil C/N decreased from 14 in
grasslands to 11 in woodlands, indicating that N accumulated relatively
faster than C. Grassland-to-woodland conversion has been geographically
wide-spread, suggesting that the ecosystem-level changes in soil C and N
storage documented here could also be important for global biogeochemistry.

Date submitted: 12/15/98